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A statistical method to predict tropospheric amplitude scintillation parameters along earth-space microwave links from meteorological data is proposed. The evaluation of the mean value and the variance of the refractive-index structure constant and of the scintillation power (i.e., the variance of the log-amplitude fluctuations of the received electromagnetic field) is carried out from conventional radio-sounding measurements. A large radio-sounding data set, collected in Northern Italy over ten years is utilized to simulate clear-air amplitude scintillation variance at microwaves and millimeter-waves on slant paths. Scintillation statistics of interest for link-budget design are also derived from the radio-sounding data set for short and long-term applications. Scintillation prediction formulas, based on measurements of surface temperature and relative humidity, are also derived and regression coefficient tables are given on an hourly and a monthly basis. Comparisons of short-term and long-term prediction results with Olympus down-link measurements at 19.8 GHz are shown and discussed. A model investigation about the statistical correlation between scintillation power and brightness temperature is performed, deriving an extension of the estimation methods to include integrated water vapor measurements from ground-based microwave radiometers.

Abstract. As a first step for remote sensing cloud properties, a database of cloud genera has been established. This is derived from a microphysical model, and it considers the statistical profiles of four hydrometeor species for each cloud genus. From this database the corresponding radiative database is obtained making use of a radiative transfer model, so for each cloud genus the simulated microwave response at the special sensor microwave imager channels is found. The cloud and radiative databases allow the retrieval of the genera of the cloud and other relevant properties from satellite observations. An automatic cloud genus classifier has also been implemented. Several tests have been carried out, and the results are presented.

We explain discrepancies in comparing estimations of the refractive-index structure constant C(n)(2) in clear air by means of different techniques by taking into account atmospheric intermittency effects. We formulate a model of C(n)(2) in intermittent turbulence on the basis of the Tatarskii theory, and we calculate the mean value of C(n)(2) through a probabilistic approach. We deduce a factor, which gives a measure of the statistical reduction of turbulence that is due to intermittency, within the model framework. A procedure for estimating the mean value of C(n)(2) from data of a specific radiosonde observation is illustrated.

A steerable dual-channel microwave radiometer was installed on top of an oceanographic tower otT shore from the Venice lagoon (Italy) during the calibration experiment of the ERS-] radar altimeter organized by the European Space Agency. Measurements of atmospheric brightness temperature were carried out over more than two months in the summer 1991. The main objective of the experiment was to obtain the tropospheric electromagnetic excess path length (fiH) required for the correction of the radar altimeter on board the satellite. The instrument calibration and the parameter retrieval algorithms were the main problems to be addressed. The retrieval of other meterological parameters, namely the precipitable water vapour (V) and the integrated cloud liquid (L), was also assessed. An accuracy (r.m.s.) of about 0·8 cm in fiH, 0·1 em in Vand 0·04mm in L is expected, resulting in a significant improvement when compared to those available from conventional meteorological data.